How Galaxies Form: New Research Resolves Conflict in Theory
ScienceDaily (Jan. 14, 2010) — For more than two decades, the cold dark matter theory has been used by cosmologists to explain how the smooth universe born in the big bang more than 13 billion years ago evolved into the filamentary, galaxy-rich cosmic web that we see today.
These images depict various stages of galaxy formation under the cold dark matter theory using new computer simulations that account for the effects of supernova explosions. (Credit: Katy Brooks)
There's been just one problem: the theory suggested most galaxies should have far more stars and dark matter at their cores than they actually do. The problem is most pronounced for dwarf galaxies, the most common galaxies in our own celestial neighborhood. Each contains less than 1 percent of the stars found in large galaxies such as the Milky Way.
Now an international research team, led by a University of Washington astronomer, reports Jan. 14 in Nature that it resolved the problem using millions of hours on supercomputers to run simulations of galaxy formation (1 million hours is more than 100 years). The simulations produced dwarf galaxies very much like those observed today by satellites and large telescopes around the world.
"Most previous work included only a simple description of how and where stars formed within galaxies, or neglected star formation altogether," said Fabio Governato, a UW research associate professor of astronomy and lead author of the Nature paper.
"Instead we performed new computer simulations, run over several national supercomputing facilities, and included a better description of where and how star formation happens in galaxies."
The simulations showed that as the most massive new stars exploded as supernovas, the blasts generated enormous winds that swept huge amounts of gas away from the center of what would become dwarf galaxies, preventing millions of new stars from forming.
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